In the future, the energy stores for vehicles and for applications in the power industry, such as, e.g., stationary energy stores, will have to have a substantially greater storage potential and a higher reliability, a substantially longer service life and, above all, a substantially higher level of safety. Li-ion/lithium metal technology has clear performance and weight advantages over other energy stores, but today, it does not yet have the necessary margin of safety.
For use, e.g., in vehicles, the safety of lithium ion batteries is a factor that is not to be neglected. In comparison with applications in mobile electronics, the chemically active mass of a traction battery is substantially higher, and therefore, the potential risk is markedly greater. Since the electrodes are protected against only a sudden reaction with the highly flammable, organic electrolytes by a passivating surface film, an operating state that promotes sudden break-up of the films, such as high temperatures, overcharging or excessive discharging, is to be prevented. Thermal breakdown of the cell from local overheating may also be initiated by internal short circuits, e.g., due to contamination during production.
In general, the safety is substantially a function of the combination of the materials actually selected for electrodes and electrolyte, as well as of the quality of the manufacturing of the cells. The traction batteries are typically made up of several hundred to several thousand individual cells, in order to provide the required range (battery capacity) and power. In practical application, the individual cells are assembled to form a spatially compact module. Normally, the cells in a module are so tightly packed that in the case of thermal breakdown of a single cell, adjacent cells may also be “ignited.” In this context, there is a risk of decomposition or destruction of the entire battery module via a chain reaction. In an extreme case, the battery module may also burn, in which case, in particular, it must be taken into account that many types of battery modules, such as lithium ion storage batteries, may not come into contact with water, in order to prevent the typical alkali metal reaction with water to form hydrogen. In this respect, anhydrous extinguishing agents must be used in the case of fire.
The Korean Patent Application KR 2006086120 describes a battery module, whose battery cells dissipate heat in a more effective manner due to modified positioning of the battery cells, and which provides cooling channels at the battery cells.
U.S. Pat. No. 5,456,994 A describes a battery module having temperature monitoring and a closed housing for use in electric vehicles. The battery modules described have a housing provided with an air inlet on the front side and an air outlet on the back side. Using partitions, the housing is divided into individual chambers, into which individual battery cells may be inserted.
International Patent Application WO 2008027343 describes a battery module for vehicles, in which battery cells are arranged in groups set apart from one another. Several battery cells are arranged inside of a housing, in two groups, which are separated from one another by a central region. The housing is configured to allow cooling air from the central region to reach the cells. In this context, each group of cells is arranged in two layers set apart relative to one another.
In conventional battery modules, due to the proximity of the individual battery cells with respect to one another, there is a risk that in the event of a thermal overload of an individual cell, adjacent cells will be detrimentally affected and thermally overloaded as well. In the extreme case, a breakdown of a cell may cause, in this case, the breakdown of further cells in a chain reaction. On the other hand, an energy density of the battery modules, which is as high as possible, is desired, which is why as many battery cells as possible must be spaced closely to one another.